While autologous vein remains the graft of choice, advanced vascular disease and prior surgical intervention limit the availability of autologous grafts. The use of synthetic grafts provides a means for restoring blood flow to ischemic areas when no alternative is available. Commercially available grafts are far from ideal due to their inherent thrombogenicity. The transplantation of a functional endothelial cell lining onto the surface of a vascular graft has proven to increase patency rates and decrease thrombus formation on the flow surface in animal models. Past and present studies have focused on the isolation of large vessel endothelial cells from vein segments, with the subsequent seeding of these cells on the graft lumenal surface. Tissue culture advances have also made the generation of large numbers of endothelial cells for high-density seeding on vascular prosthesis possible. These techniques have major drawbacks in the clinical setting. Endothelialization occurs at a slow rate when low density seeding techniques are applied. High-density seeding, using cultured endothelial cells requires the use of undefined media, not easily applicable to the clinical setting.
To overcome the problems associated with seeding large vessel endothelial cells on prosthetic grafts, methods for the isolation of microvessel endothelial cells from autologous adipose tissue followed by high density seeding of a vascular prosthesis were developed.
Although microvessel endothelial cells have been shown to be capable of endothelializing a blood-contacting surface, methods of procuring and depositing these cells in an operating room setting present special considerations. Methods currently used employ standard laboratory equipment such as beakers, flasks, centrifuge tubes, shaker baths, pipettes, syringes, sterile hoods. For example, in Williams' and Jarrell's U.S. Pat. No. 4,820,626 and related applications, methods of treating a graft surface with endothelial cells are disclosed. According to those methods, subcutaneous adipose tissue is aspirated via a cannula and transferred by vacuum into a mucous trap. The trap is then transferred to a sterile hood for further processing. Adipose tissue is transferred to a sieve inside a funnel which is placed in a sterile beaker. A rinsing solution is then poured over the tissue to remove red blood cells and lysed fat. The tissue is manually poured into a sterile Erlenmeyer flask containing collagenase solution and agitated at 37.degree. C. for 20 minutes. The collagenase slurry is manually poured into sterile conical centrifuge tubes and spun for seven minutes at 700.times.G. The endothelial cells ar then pipetted out of the tube. A graft is tied to a male luer extension and secured within a tube. The cells are resuspended in serum protein media and drawn into a syringe. Using a needle and a syringe, the cells are forced into the lumen of the graft. The graft is manually rotated for 2 hours.
In spite of these advances, a need still exists for a simple, reliable method of producing endothelial cell coatings on a graft in a operating room setting.